This study examined the relationship between executive functions (EFs) and school performance in primary and secondary school students aged 8 to 13 years (N = 146, M = 10.4, 45.8% girls). EFs were evaluated using the Trail Making Test (TMT), Verbal Fluency (VF), and the Stroop Test. Students’ GPAs and teachers’ assessment of academic skills were used to measure school performance. To evaluate the students’ social behavior, participants were asked to rate all their classmates’ prosocial behavior and nominate three students with whom they preferred to do school activities; teachers also provided evaluations of students’ social skills. EF measures explained 41% (p = .003, f2 = .694) of variability in school performance and 29% (p = .005, f2 = .401) of variance in social behavior in primary school students. The predictive power of EFs was found to be lower for secondary school students, although the TMT showed significant prediction and explained 13% (p = .004, f2 = .149) of variance in school performance and 15% (p = .008, f2 = .176) in peer ratings of prosocial behavior. This paper discusses the relevance of EFs in the school environment and their different predictive power in primary and secondary school students.